1. Field of the Invention
The present invention relates to a low-resistance semiconductor layer, a method of manufacturing the same, a laser diode including a low-resistance semiconductor layer, and a method of manufacturing the same.
2. Description of the Related Art
In the past, a phenomenon that in a p-type semiconductor crystal material, by bonding a hydrogen atom with p-type impurity, the p-type impurity is inactivated, and the carrier concentration is lowered has been known. Lowering of the carrier concentration causes high resistance, and leads to lowering life due to heat generation at the time of operation, that is, lowering of reliability. Hydrogen incorporation at the time of temperature drop after growth makes it difficult to realize a long-term stable laser operation.
The inactivation of the p-type impurity is caused by an event that hydrogen radical generated from arsine (AsH3) is taken into crystal at the time of temperature drop after growth (see Japanese Patent No. 3553147). Thus, to obtain a desired carrier concentration, semiconductor should be doped with impurity beyond necessity. However, if the semiconductor is doped with impurity beyond necessity, the impurity is diffused into an active layer, or crystal defect in the p-type semiconductor is increased. In the result, there is concern that laser reliability is impaired.
Several methods to inhibit such inactivation of the p-type impurity have been already proposed. For example, in Japanese Patent No. 3553147, a method to change AsH3 supplied at the time of temperature drop after growth to an organic Group V (TMAs, TBA or the like) is proposed. In the method, by using the organic Group V raw material not generating hydrogen radical instead of AsH3 at the time of temperature drop after growth when hydrogen is mixed, inactivation of the p-type impurity is able to be inhibited. A similar method is described in Japanese Unexamined Patent Application Publication No. 2000-316000 as well. In Japanese Unexamined Patent Application Publication No. 2000-316000, to prevent hydrogen incorporation from AsH3, nitrogen is used instead of the organic Group V at the time of temperature drop after growth.